I have a 2012 Honda Civic LX, and I have put three new remained alternators in the last month. My lights would start to fluctuate, so I went in and had the store test it, and it would show a failure on the voltage regulator. But when I turn on the headlights, it would pass everything. Is there something else that could be causing this failure?

Answer

I don't have the manual for this model with me, but I believe the ECM controls the output. There could be a fault in either the control circuit, one of the sensors the ECM uses to compute the output, or the ECM itself.

Updated on April 3, 2018

Original Article:

Troubleshooting Alternator and Charging System Problems
By Dan Ferrell
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